1. Technical Field
This invention generally relates to transportation vehicles. More particularly, the invention relates to vehicles having an open-top cargo box that is selectively coverable with a bow-supported tarpaulin. Specifically, the invention relates to a cargo box that has a plurality of apertures formed in an upper surface of the side walls and which are sized to loosely receive the ends of the tarpaulin bows therein so as to permit lateral sliding motion of the ends within the apertures if the side walls spread apart under pressure exerted by a load carried in the cargo box.
2. Background Information
In the United States, trucks are used to transport a wide variety of goods from one side of the country to the other. Some of these trucks are of the type having an open cargo box or trailer into which the goods are placed. Tarpaulin systems may be used on these trailers to cover the loads therein during transportation of the same. This is especially true of loads such as grain or sand where the tarpaulin both prevents granules from blowing out of the trailer and protects the load from the elements.
A wide variety of tarpaulin systems are available for this purpose including systems in which a tarpaulin is supported across the trailer opening by a plurality of bows or ribs. The bows typically have an arcuate portion with downwardly extending first and second ends. In U.S. Pat. No. 4,854,633, issued to Kraft et al, the first end of each bow is received in a recess formed in the upper rail of the trailer and the second end of the bow is received in a retaining ring provided on the opposite upper rail. A locking mechanism is provided to rigidly secure the second ends of the bows in place and substantially prevent them from being moving or becoming disengaged from the second upper rail. As shown in the drawings of the patent, both the first and second ends of the bows are tightly received within the recess and retaining ring to secure the bows to the trailer body.
U.S. Pat. No. 2,955,874, issued to Brindley, show tarpaulin bows in which the downwardly extending first and second legs are tightly received within tubular sockets disposed between the inner and outer walls of the trailer body.
U.S. Pat. No. 4,248,475, issued to Johnsen, shows the first and second ends of the bows each being tightly retained in an aperture formed between an U-shaped flange and the side of one of the first and second upper rails. Once again, the first and second ends of the bows are tightly received within the apertures and are thereby prevented from moving in any direction within the apertures.
U.S. Pat. No. 3,971,590, issued to Yglesias, discloses a trailer in which recesses are formed in the upper rails and a sleeve is inserted into each recess. The downwardly extending first and second ends of the bows are tightly received within the bores of the sleeves, thereby firmly retaining the bows in place.
Similarly, in the tarpaulin system disclosed in U.S. Pat. No. 3,384,413, issued to Sargent, each of the first and second ends of the bows are tightly received within a sleeve that is itself tightly received within a recess in the upper rails. A similar system is also found in U.S. Pat. No. 5,664,824 to Stephens et al; U.S. Pat. No. 3,226,153 to Haid, and U.S. Pat. No. 3,126,224 to Carter Jr. et al.
While these systems all work adequately for the purpose for which they were intended, in some instances, the bows used in these tarpaulin systems will be prone to damage and failure. This is especially true when the trailer is between fifty and eighty feet long and is used to transport loads such as grain or sand. Grain or sand tends to spread out within the cargo box of a railer and bring a substantial amount of pressure to bear upon the side walls. The pressure may be great enough to cause the side walls to bow outwardly by as much as one inch. When the first and second ends of the bows are secured in any of the ways disclosed in the previously mentioned patents, the bowing of the side walls tends to damage or break either the ends of the bows or the sleeves or flanges in which they are retained. Furthermore, the distortion in the walls frequently prevents the removal of the damaged components until after the grain or sand has been unloaded from the trailer.
There is therefore a need in the art for an improved mechanism for securing a tarpaulin system to a long bed open-top truck trailer that reduces the likelihood of breakage of the bows during transport of loads such as grain or sand.